In principle, it is known that springs, preferably gas pressurized springs, can be used to assist the movement of typically heavy panels or doors in motor vehicles. However, gas pressurized springs have the drawback that the support moment that can be applied varies as a function of the ambient temperature, because the pressure of the working gas in the interior of the gas pressurized spring varies. The result is that such sprung panels or doors are harder to open in the winter and are harder to close in the summer. Furthermore, the torque that has to be applied for the movement of the panel or door varies as a function of the instantaneous pivot position. For example, when the rear hatch leaves its closed position, the torque increases until the rear hatch reaches its horizontal position that is characterized by a maximum torque, whereas when the rear hatch continues to pivot in the direction of the open position, the effective torque decreases. Since as a rule only spring elements exhibiting a linear force/travel characteristic are available, the curved flow of the torque of the panel or door cannot be adequately compensated.
DE 4104125 A1 describes a passenger vehicle having a rear hatch that is hinged to a roof railing by means of two hinges. In this case, each of the two hinges is coupled with a foot of the roof railing and connected to a respective torsion bar spring. The torsion bar spring extends in each case from one foot of the roof railing to the opposite foot. The torsion bar springs help open the rear hatch. In the closed position of the rear hatch, the torsion bar springs are prestressed; and this tension is used, after unlocking, to move the rear hatch into the open position.
DE 3023950 A1 shows a device for adjusting the prestress of torsion bar springs that serve to balance the weight of pivotable body components, like rear hatches, wherein the respective end-sided, moved working section engages with the rear hatch; and an opposite support section is supported on the body side. A ratchet mechanism with a pawl wheel, which can be connected in a torque transmitting manner to one of the bar sections, and with a lock pawl, which can be mounted in a rotationally rigid manner on the body, permits a static adaptation of the torsional moment, which is applied by the torsion bar springs and which counteracts the torque of the rear hatch in the course of opening and closing the same.
With such devices, it is possible to statically vary the torsional moment on a small scale, as a result of which variable assistance in the course of actuating the rear hatch is possible. However, in almost all opening positions of the rear hatch there is a difference between the actual torque of the rear hatch and the adjusted torsional moment of the torsion bar springs, wherein said torsional moment assumes inconveniently high actuating forces over the entire opening path.
Therefore, the object of the present invention is to provide a motor vehicle with a panel or door that keeps the necessary actuating forces for opening or closing the panel or door as low as possible with a relatively compact and robust mechanism.